This section provides background information related to the present disclosure which is not necessarily prior art.
Most automobiles in current use are driven by fuel engines which experience a great deal of mechanical loss and have low energy efficiency, thereby consuming a lot of energy and causing environmental pollution. Electric vehicles operate using stored electric energy for powering an electric motor. As battery technology has improved, the popularity of hybrid electric and electric vehicles has increased over the last several years. However, the packaging requirements for traditional electric motor drive systems have influenced the vehicle designs and efficiency.
Vehicle packaging is continually pushing for increased torque density, which presents increased risk of overvoltage of the system during uncontrolled generation. The electric drive unit of the present disclosure combines one passive one-way clutch with a selectable one-way clutch to achieve a high drive ratio, high-speed regeneration capability, and fast shift times, while significantly reducing the risk of overvoltage.
A powertrain includes an electric motor and a first planetary gear stage having a first rotatable member drivingly connected to the electric motor and at least one second rotatable member. A second planetary gear stage includes a third rotatable member drivingly connected to the at least one second rotatable member and includes at least one fourth rotatable member. One of the third rotatable member and the at least one fourth rotatable member is connected to an output member. A passive one-way clutch and a selectable one-way clutch are associated with at least one of the first and second planetary gear stages for varying operation of the first and second planetary gear stages based upon an operation state of the selectable one-way clutch and a direction of rotation of the electric motor. This results in a high ratio in the positive torque (drive) direction and a lower ratio in the negative torque (regeneration) direction. The selectable one-way clutch is a 2-state device that is opened to allow driving in the reverse direction or to reduce system losses at high speeds. By having the selectable one-way clutch closed, the system can provide torque for all-wheel-drive maneuvering without actuation delay. In the case of uncontrolled generation, the system goes into a negative torque case, loading the passive one-way clutch and the ratio is reduced automatically. This significantly reduces the risk of over voltage.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.